Most prior inventory accounting methods have shortcomings at the input end. Often, inventory is initially taken manually. From then on, constant inventory accounting is maintained by accurate accounting of all transactions into and out of stock. However, that type of inventory accounting is slow, expensive, and requires meticulous acquisition and handling of inventory data. Often the inventory derived by the constant accounting of transactions into and out of stock is inaccurate because of unaccounted for transactions, spoilage, breakage, pilferage, improper identification of number or type of goods in stock, or for other reasons. Accordingly, means have been devised for accurately determining how many items are present at selected storage sites.
U.S. Pat. No. 4,419,734 issued Dec. 6, 1983 to Wolfson et al. is an example of a shelf weight sensing apparatus that analyzes solenoid signals produced by a weight sensor. The weight sensor is attached to a shelf in order to determine the precise number of inventory items located on the specified shelf. This type of system is expensive because it requires extensive circuitry for analyzing the signals received from multiple weight sensors. In addition, this type of system is made for stationary shelving systems which is not conducive to other forms of inventory storage and control.
Therefore, there exists an unmet need to provide a low-cost weight sensing inventory control system for moveable shelves or drawers.